Composition of the Ocean — Passage and Quiz

The ocean is a complex mixture of water, salts, gases, and organic matter. Its composition varies depending on location, depth, and temperature, but it is primarily made up of water (96.5%) and dissolved salts (3.5%).

The most abundant salt in seawater is sodium chloride (table salt), but it also contains magnesium, calcium, and potassium. These salts come from the weathering of rocks on land and volcanic activity.

The ocean also contains dissolved gases like oxygen, carbon dioxide, and nitrogen. Oxygen is essential for marine life, while carbon dioxide plays a role in regulating the Earth’s climate.

Organic matter in the ocean includes plankton, algae, and marine organisms. These organisms form the base of the marine food web and contribute to the ocean’s nutrient cycle.

The ocean’s composition changes with depth. Surface waters are warmer and richer in oxygen, while deep waters are colder and contain more nutrients. Ocean currents and upwelling also redistribute heat and nutrients, influencing marine ecosystems.

Fun fact: If all the salt in the ocean were spread evenly over the Earth’s land surface, it would form a layer over 500 feet thick!